1. Field of the Invention
The present invention relates to a torsional vibration damper for arrangement in a clutch disk including a hub element, a hub-disk arrangement carried on the hub element, the hub-disk arrangement including a first transmission arrangement and a second transmission arrangement rotatable about an axis of rotation relative to the first transmission arrangement, a first damping arrangement acting between the first and the second transmission arrangement, a third transmission arrangement connected in a rotationally fixed manner to the hub element, a second damping arrangement which acts between the third transmission arrangement and one of the first and second transmission arrangements and allows a relative rotation between the third transmission arrangement and the one of the first and second transmission arrangements, and a first friction device acting between the third transmission arrangement and at least one transmission arrangement of the first and second transmission arrangements.
2. Description of the Related Art
Reference DE 33 13 850 A1 discloses a clutch disk which contains a torsional vibration damper constructed with a hub element, a hub-disk arrangement carried on the hub element, the hub-disk arrangement including a first transmission arrangement and a second transmission arrangement rotatable about an axis of rotation relative to the first transmission arrangement, a first damping arrangement acting between the first and the second transmission arrangement, a third transmission arrangement connected in a rotationally fixed manner to the hub element, a second damping arrangement which acts between the third transmission arrangement and one of the first and second transmission arrangements and allows a relative rotation between the third transmission arrangement and the one of the first and second transmission arrangements, and a first friction device acting between the third transmission arrangement and at least one transmission arrangement of the first and second transmission arrangements.
In this reference, the third transmission arrangement is formed by a disk-type area which is formed integrally with a hub element and projects radially outward. The second transmission arrangement is formed by a hub-disk element having two sheet-metal elements. A radially inner area of the second transmission arrangement surrounds both axial sides of the first transmission arrangement. A damping-spring arrangement acts between the second transmission arrangement formed by the two sheet-metal parts and the third transmission arrangement formed by the disk-type area for allowing relative rotation of these two transmission arrangements with respect to one another in the idling range.
The second transmission arrangement is mounted radially on the hub element and one of the sheet-metal parts of the second transmission arrangement is supported axially against one axial side of the third transmission arrangement via a friction ring. A preloading spring is supported against the other one of the sheet-metal parts of the second transmission arrangement via an intermediate ring and on the other axial side of the third transmission arrangement. The friction ring, the intermediate ring and the preloading spring provide a friction device which acts between the second and third transmission arrangements. In the idling range, the friction ring converts vibrational energy into friction work and thus contributes to the damping of torsional vibrations.
It is an object of the present invention to provide a torsional vibration damper with improved capability for tuning to vibration characteristics that occur in particular drive systems, especially in the idling or predamping range.
According to the present invention, the object is achieved by a torsional vibration damper for arrangement in a clutch disk, comprising a hub element and a hub-disk arrangement carried on the hub element. The hub disk arrangement comprises a first transmission arrangement and a second transmission arrangement which is rotatable about an axis of rotation relative to the first transmission arrangement. A first damping arrangement such as, for example, a damping-spring arrangement acts between the first and the second transmission arrangement. A third transmission arrangement is arranged on the hub element in a rotationally fixed manner or may alternatively comprise an integral part with the hub element. A second damping arrangement such as, for example, a damping-spring arrangement acts between the third transmission arrangement and one of the first and second transmission arrangements. The second damping arrangement allows a relative rotation between the third transmission arrangement and the one of the first and second transmission arrangements. A first friction device acts between the third transmission arrangement and at least one transmission arrangement of the first and second transmission arrangements.
In the torsional vibration damper according to the present invention, the first friction device includes a first friction-device area which generates essentially no frictional force in an angular range of relative rotation between the third transmission arrangement and the at least one transmission arrangement of the first and second transmission arrangements and generates a frictional force when the angular range of relative rotation is exceeded. The angular range starts from a basic relative rotational position between the third transmission arrangement and the at least one transmission arrangement of the first and second transmission arrangements.
This arrangement allows the friction device to act parallel to the second damping arrangement. A characteristic of the friction device is that a significant rise in the frictional force is generated from a particular angle of relative rotation onwardxe2x80x94that is to say there is a delayed friction characteristicxe2x80x94for obtaining improved tunability to particular vibrations or particular drive systems. In addition to the strength of the frictional force generated, the magnitude of the adjustable angular ranges of relative rotation represents a further parameter that may be varied for the purpose of tuning to particular systems.
In a preferred embodiment of the present invention, the first friction-device area of the first friction device is effective only between the third transmission arrangement and that transmission arrangement of the first and second transmission arrangements which interacts with the second damper arrangement.
The ability to tune to the particular requirements of a specific application of the torsional vibration damper may be improved further if the first friction device further comprises a second friction-device area which generates a frictional force essentially independently of the relative rotational position of the third transmission arrangement and the at least one transmission arrangement of the first and second transmission arrangements. In this embodiment, a basic friction is already being generated within the angular range of relative rotation. The basic friction is then increased further by the first friction-device area when the angular range of relative rotation is exceeded.
The torsional vibration damper according to the present invention for the first friction-device area comprises a friction-element arrangement which rests under preload against the third transmission arrangement and/or the at least one transmission arrangement of the first and second transmission arrangements. The friction-element arrangement may comprise at least one friction element which rubs against the third transmission arrangement and/or the at least one transmission arrangement of the first and second transmission arrangements. This friction element may rub against the at least one transmission arrangement of the first and second transmission arrangements and may be coupled or connectable in a rotationally fixed manner to the third transmission arrangement.
The delayed-action friction characteristic may be obtained in a simple manner by arranging the at least one friction element so that it is freely rotatable relative to the third transmission arrangement in an angular range of relative rotation between the third transmission arrangement and the at least one transmission arrangement of the first and second transmission arrangements and so that the at least one friction element is coupled to the third transmission arrangement when the angular range of relative rotation is exceeded. The at least one friction element is freely rotatable starting from a basic relative rotational position between the third transmission arrangement and the at least one transmission arrangement of the first and second transmission arrangements.
For optimizing the utilization of installation space, the preferred embodiment includes an area of the transmission arrangement of the first and second transmission arrangements that interacts with the second damping arrangement that has a respective disk area axially on each side of the third transmission arrangement, wherein the first friction device rubs against at least one of the disk areas. This arrangement may be achieved, for example, if the at least one transmission arrangement of the first and second transmission arrangements is of essentially symmetrical construction in both axial directions relative to the third transmission arrangement.
The structure of the torsional vibration damper according to the invention may, for example, be arranged such that the at least one transmission arrangement of the first and second transmission arrangements has at least two disk parts which, in their area which interacts with the second damping arrangement and is intended for the provision of the two disk areas, are spaced apart axially and are connected to one another radially to the outside of the disk areas. In their interconnected area, the two disk parts may be designed to interact with the first damping arrangement.
To achieve suitable centering of the hub-disk arrangement of the torsional vibration damper according to the invention relative to the hub element, the present invention furthermore provides a bearing arrangement via which the hub-disk arrangement is mounted on the hub element. The bearing arrangement is preloaded into bearing engagement on the hub element by a first preloading arrangement and comprises a bearing ring with an essentially conical, spherical or similar bearing surface via which the bearing ring is preloaded into bearing engagement against a mating bearing surface of essentially complementary form on the hub element. To allow a friction device also to act in parallel with the second damping device, which is generally a main and load damping device, i.e. to dissipate vibrational energy by producing friction work in the range of onset of the load damper range, the torsional vibration damper according to the present invention further comprises a second friction device for generating a frictional damping force during relative rotation between the first and the second transmission arrangement. The second friction device comprising at least one friction element which is acted upon by a preloading arrangement and is displaceable on the first transmission arrangement and/or the second transmission arrangement during relative rotation, thereby generating a frictional damping force.
The structure of the torsional vibration damper according to the invention may be simplified if the bearing arrangement forms at least a portion of the at least one friction element of the second friction device.
The one transmission arrangement of the first and second transmission arrangements may comprise a disk transmission arrangement and the other transmission arrangement of the first and second transmission arrangements may comprise first and second cover-disk elements arranged on opposing axial sides of the disk transmission arrangement. The first and second cover-disk elements are connected to one another in a rotationally fixed manner and a friction area of the bearing arrangement lies between the disk transmission arrangement and one of the cover-disk elements of the other transmission arrangement.
The force return path is within the torsional vibration damper if the preloading arrangement acts between the disk-type transmission arrangement and the other one of the cover-disk elements and preloads the disk-type transmission arrangement towards said one cover-disk element such that the friction area of the bearing arrangement is clamped between the disk-type transmission arrangement and the cover-disk element to generate the frictional damping force.
For example, the bearing ring may be connected in a rotationally fixed manner to either the first transmission arrangement or the second transmission arrangement.
For this purpose, the bearing ring may comprise at least one coupling portion, via which it is coupled to the first transmission arrangement or the second transmission arrangement.
The torsional vibration damper according to the present invention is furthermore preferably provided with a preloading arrangement which preloads the bearing ring into the bearing engagement so that it is supported against the hub element and against the one of the first and second transmission arrangements on which the bearing arrangement can be displaced, thereby generating the frictional damping force. The preloading arrangement may be supported against the other cover-disk element of the other of the first and second transmission arrangements.
The present invention furthermore relates to a clutch disk which includes a torsional vibration damper according to the present invention.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.